The present invention relates to model trains, and in particular force sensors for model trains.
A variety of control systems are used to control model trains. In one system, the power to the track is increased, or decreased, to control the speed and direction of the train. Multiple trains can be controlled by providing different power levels to the different sections of the track having different trains.
In another type of control system, a coded signal is sent along the track, and addressed to the desired train, giving it commands such as speed and direction. The train itself controls its speed by converting the AC voltage on the track into the desired DC motor voltage for the train according to the received instructions. The instructions can also tell the train to turn on or off its lights, horns, etc. U.S. Pat. Nos. 5,441,223 and 5,749,547 issued to Neil Young et al. show such a system.
FIG. 1A is a perspective drawing of an example layout of a conventional model train system allowing the communication of signals from a base unit to a locomotive and other components.
A hand-held remote control unit 12 is used to transmit signals to a base unit 14 and to a power master unit 150 both of which are connected to train tracks 16. Base unit 14 receives power through an AC adapter 18. A separate transformer 20 is connected to track 16 to apply power to the tracks through power master unit 150. Power master unit 150 is used to control the delivery of power to the track 16 and also is used to superimpose DC control signals on the AC power signal upon request by command signals from control unit 12.
Power master unit 150 modulates AC track power to the track 16 and also superimposes DC control signals on the track to control special effects and locomotive 24′. Locomotive 24′ is, e.g., a standard Lionel locomotive powered by AC track power and receptive to DC control signals for, e.g., sound effects.
455 kHz transmitter 33 of base unit 14 is configured to transmit an outgoing RF signal between the track and earth ground, which generates an electromagnetic field indicated by lines 22 which propagates along the track. This field will pass through a locomotive 24 and will be received by a capacity antenna located inside the locomotive.
FIG. 1B is a simplified schematic drawing of the conventional system shown in FIG. 1A. FIG. 1B shows a cross-sectional view of locomotive 24, which may be, e.g., a standard locomotive retrofitted or designed to carry antenna 26. The signal will then be communicated from antenna 26 to 455 kHz receiver 37 of engine 24. Locomotive 26 further includes a processor 84 in communication with receiver 37 and configured to interpret the received signal.
Returning to FIG. 1A, receipt of control signals is not limited to moving elements of the train set. The electromagnetic field generated by base unit 14 will also propagate along a line 28 to a switch controller 30. Switch controller 30 also has a receiver in it, and will itself transmit control signals to various devices, such as the track switching module 32 or a moving flag 34.
The use of both base unit 14 and power master unit 150 allows operation and control of several types of locomotives on a single track layout. Locomotives 24 which have been retrofitted or designed to carry receiver 26 are receptive to control signals delivered via base unit 14. Standard locomotives 24′ which have not been so retrofitted may be controlled using DC offset signals produced by power master unit 150.
The remote unit can transmit commands wirelessly to base unit 14, power master unit 150, accessories such as accessory 31, and could transmit directly to train engines instead of through the tracks. Such a transmission directly to the train engine could be used for newer engines with a wireless receiver, while older train engines would continue to receive commands through the tracks.
Regarding force sensors, one type of pressure-sensitive input element is a resistor which senses force, such as the Force Sensing Resistor® (FSR®) available from Interlink Electronics. Such a resistor typically includes two conductors mounted on spaced apart substrates, with the substrates being compressed to close the gap and provide contact between the conductors. The signal output varies in accordance with the area of contact. An example is set forth in Interlink U.S. Pat. No. 5,302,936. Another pressure-sensitive force transducer is described in U.S. Pat. No. 4,489,302.